The present invention is a process for preparing silanes by the reaction of silicon monoxide with organic halides, in the presence of a catalyst. The described catalysts increase conversion of the silicon monoxide and alter the selectivity of the described processes for silane products. Selectivity for product silanes can be furthered altered by an activation step comprising the heating of the silicon monoxide in an inert atmosphere.
Silanes are primarily produced by the direct reacting of silicon with organic halides or hydrogen halides, as first disclosed by Rochow and his co-workers in the 1940's. A significant portion of the cost of this process is the cost of the silicon metal used as a feed material. Silicon metal is typically produced in an electric-arc furnace by the carbothermic reduction of silicon dioxide. This process requires high temperature and high energy consumption, which is reflected in the cost of silicon metal.
Silicon monoxide can be produced at a lower temperature than silicon and, thus, may serve as a less expensive raw material for the production of silanes. The instant invention describes a process whereby potentially less expensive solid silicon monoxide can be reacted with alkyl halides to produce silanes.
Schaschel, in a series of patents, described a process for preparing organosilicon polymers by reacting silicon monoxide with organic compounds. The methods of the described invention involved preparation of silicon monoxide vapors from solid silicon monoxide by heating the same under vacuum to about 1200.degree. C. to 1300.degree. C.; mixing in a chamber having cooled walls the gaseous silicon monoxide formed thereby, with an excess of a volatile organic compound to form a mixture; and condensing the mixture to obtain the organosilicon polymer. The reaction is reported to occur on the cold surface of the chamber to form the polymer thereon.
The reactions of organic compounds taught by Schaschel are: Schaschel, U.S. Pat. No. 3,660,448, issued May 2, 1972, organic compounds containing active hydrogen atoms such as alcohols and amines; Schaschel, U.S. Pat. No. 3,660,449, issued May 2, 1972, organic compounds containing a triple bond such as acetylene; Schaschel, U.S. Pat. No. 3,660,451, issued May 2, 1972, organic monohalides such as 1-bromobutane; and Schaschel, U.S. Pat. No. 3,661,961, issued May 9, 1972, aliphatic hydrocarbons such as n-octane.
Timms, U.S. Pat. No. 3,660,450, issued May 2, 1972, teaches a process for reacting gaseous silicon monoxide with an aromatic compound containing at least one benzene nucleus, the compound having no triple bonds and having no active hydrogen atoms. The described process is similar to that previously described for the Schaschel series of patents.
Gomberg, U.S. Pat. No. 4,585,646, issued April 29, 1986, teaches a process where Si.sub.2 OCl.sub.6 is irradiated to form solid SiO. The solid SiO is isolated and reacted at 500.degree. C. with HCl. The process is reported to form tetrachlorosilane, water, and hydrogen gas. No SiH products were produced. In addition, no activation process for the silicon monoxide or use of a catalyst is taught.